안녕하세요.
현재로서는 다음과 같이 preference를 바꿀수 있습니다.
mConnectivityManager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);
mConnectivityManager.setNetworkPreference(ConnectivityManager.TYPE_MOBILE);
하지만 doc에서 guide 하듯이 곧 deprecate될 API 입니다.
public void setNetworkPreference (int preference)
Specifies the preferred network type. When the device has more than one type available the preferred network type will be used. Note that this made sense when we only had 2 network types, but with more and more default networks we need an array to list their ordering. This will be deprecated soon.